Many food products, such as fruit juice, pasteurized or UHT (ultra-high-temperature treated) milk, wine, tomato sauce, etc., are sold in packages made of sterilized packaging material.
A typical example of this type of package is the parallelepiped-shaped package for liquid or pourable food products known as Tetra Brik Aseptic (registered trademark), which is made by folding and sealing laminated strip packaging material.
The packaging material has a multilayer structure substantially comprising a base layer for stiffness and strength, which may be defined by a layer of fibrous material, e.g. paper, or mineral-filled polypropylene material; and a number of layers of heat-seal plastic material, e.g. polyethylene film, covering both sides of the base layer.
In the case of aseptic packages for long-storage products, such as UHT milk, the packaging material also comprises a layer of gas- and light-barrier material, e.g. aluminium foil or ethyl vinyl alcohol (EVOH) film, which is superimposed on a layer of heat-seal plastic material, and is in turn covered with another layer of heat-seal plastic material forming the inner face of the package eventually contacting the food product.
As is known, packages of this sort are produced on fully automatic packaging units having a supply station fed with reels of sheet packaging material.
In greater detail, a pair of reels is mounted on the supply station, and each reel has a hollow core mounted on a spindle.
More precisely, a first reel is processed by the packaging unit while a new second reel is mounted on supply station and remains idle during the operation of the packaging unit.
During the operation of the packaging unit, the packaging material of the first reel slides within a slot defined by a first packaging material holder connected to a fixed part of the supply station.
In particular, a continuous tube is formed from the web-fed packaging material in the packaging unit; the web of packaging material is sterilized in the packaging unit, e.g. by applying a chemical sterilizing agent such as a hydrogen peroxide solution, which is subsequently removed, e.g. by heating and evaporation, from the surfaces of the packaging material.
The sterilized web is maintained in a closed, sterile environment, and is folded into a cylinder and sealed longitudinally to form a tube.
The tube is fed in a first vertical direction parallel to its axis, is filled continuously with the sterilized or sterile-processed food product and is heat-sealed at equally spaced cross sections by two pairs of jaws to form pillow packs each having a top and a bottom transverse sealing band, i.e. a band extending along a second direction orthogonal to the first direction. Pillow packs are separated by cutting respective sealing bands and are then fed to a folding station, in which they are fold so as to form respective packages.
When the packaging material of the first reel is almost totally unwound from the core and almost all of the packaging material has passed through the slot of the first packaging material holder, a head movable within the supply station cuts the packaging material immediately downstream from the first packaging material holder. In this way, a first edge of the packaging material of the terminated first reel overhangs from the first packaging material holder while a second edge of the packaging material of the terminated first reel remains within the supply station of the packaging unit. In particular, first and second edge are parallel and spaced one another.
As packaging unit processes first reel, an operator inserts an end portion of the new second reel within the slot of a second packaging material holder, so that such end portion overhangs from such second packaging material holder.
Furthermore, the operator carries out a plurality of operations preliminary for the joining of the end portion of the new second reel to the second edge of the packaging material of the terminated first reel.
More precisely, the operator arranges, at the supply station, the end portion of the new second reel in the correct position with respect to the second packaging material holder and cuts the end portion along a slanted line. In this way, the operator forms a third edge of the new second reel; such third edge is positioned and shaped so as to perfectly match the second edge of the first reel.
At the end of these preliminary operations, third edge of the second reel overhangs from second packaging material holder connected to a fixed part of the supply station.
After having cut packaging material of first reel, head welds the second edge of the first reel to the third edge of the new second reel, so that the operation of packaging unit may continue processing the packaging material of the new second reel.
In a second time, the operator removes the core of the terminated first reel together with the packaging material extending between the core and the first edge, and feeds the supply station with a further new reel of packaging material.
A need is felt within the industry to meet the tolerance requirements for the joining of the second edge of terminated first reel to the third edge of new second reel while reducing, or even eliminating, the presence of operators at the supply station of the packaging unit.